Commitments and Contingencies - Summary Of Changes In Accrued Environmental Liabilities - (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accrual For Environmental Loss Contingencies
Accrual for Environmental Loss Contingencies, Beginning Balance	$ 15.6	$ 16.0
Environmental liabilities assumed in business combination			$ 15.3
Revisions and liabilities incurred	(2.1)	0.1	1.0
Payments		(0.4)
Currency translation adjustments and other charges	0.2	(0.1)	(0.3)
Accrual for Environmental Loss Contingencies, Ending Balance	13.7	15.6	16.0
Less amount classified as accrued liabilities	(3.3)	(4.0)	(4.3)
Environmental liabilities	$ 10.4	$ 11.6	$ 11.7